I fully comprehend the tradeoff here though, particularly when it comes to tight deadlines and weight tolerances. The CO2 scrubber in the CSM didn't need to be as beefy as the one in the LEM, and the two air filtration systems were designed by different companies where coordination would have been a bitch.
It's the classic software engineering trade off, isn't it? Add more dependencies or DIY. I wonder how the ISS deals with this in the US vs Russian parts of the station?